In many of the image forming apparatuses using the electrophotographic process, a sheet carrying a toner image is pressed and heated by the fixing section provided with an oppositely arranged roller or belt, whereby the image is fixed onto the sheet.
The roller or belt used in such a fixing section is heavily pressed against the sheet at the time of fixing operation. The surface of the roller or belt may be scratched, and the scratch may be reflected on the image on the sheet.
The aforementioned scratch often occurs in the area where the surface of the roller or belt and the respective ends, of the sheet, in the traveling direction (hereinafter referred to as “side end” for short) come in contact frequently. Thus, a scratch generated on the surface of the roller or belt by the contact with the side end of the smaller-sized sheet will appears on a fixed image when that image is formed on a larger-sized sheet.
In one of the proposed techniques to reduce the occurrence of scratches on the surface of the roller or belt, the roller or belt is moved in a direction perpendicular to the traveling direction of sheets, thereby preventing the side end of the sheets from repeatedly contacting a particular area on the surface of the roller or belt (Patent Documents 1 and 2).
However, the scratches appear on the surface of the roller or belt have a characteristic distribution of their positions of occurrence. A desired advantage may not be obtained by the technical means in which the contact area where the side ends of the sheets contact with the roller or belt by moving the roller or belt in a direction perpendicular to the traveling direction of sheets at a predetermined pitch or at a uniform speed.